French cartoonist Charb, publishing director of French satirical weekly Charlie Hebdo, poses for photographs at their offices in Paris REUTERS/Jacky Naegelen

French police in the western city of La Rochelle have detained a man suspected of threatening to decapitate the editor of a French satirical weekly that published lewd caricatures of the Prophet Muhammad.

Sipa news agency reported that a 43-year-old man was detained today for questioning after the prosecutor's office opened a probe over the threat, made in an Internet forum, against the editor-in-chief of Charlie Hebdo magazine.

Wednesday's publication of the cartoons by Charlie Hebdo has raised concerns that French interests worldwide could face violent protests like the ones targeting the US over an anti-Islam video produced in California that mocked Muhammad.